Effects of High-Volume bottom ash on Strength, Shrinkage, and creep of High-Strength recycled concrete aggregate

Abstract

This research investigated the use of high-volume bottom ash in high-strength concrete containing recycled coarse aggregate (RCA). Bottom ash received directly from a power plant was sieved to separate it into two grades: 1) bottom ash that passed through a No. 50 sieve (FBA) and 2) bottom ash that passed through a No. 4 sieve and was retained on a No. 50 sieve (CBA). Then, FBA was ground to a fine powder (G-FBA) and used to replace Portland cement at 35 %–65 % by weight of binder. Also, CBA was used as a fine aggregate replacement at 50 and 100 % by volume. All high-strength concretes were tested to determine the compressive strength, elastic modulus, total shrinkage, and compression creep. The results showed that concrete containing 100 % RCA (RA concrete) had compressive strength reduced by about 10 % compared with conventional concrete (CT concrete). However, the use of high-volume G-FBA (35 to 65 % by binder weight) improved the compressive strength of concrete in the long term due to the influence of RCA. When G-FBA replaced 50 % of the ordinary Portland cement (OPC), the compressive strength of the resulting concrete was the same as that of CT concrete at 90 days, up to 94.5 MPa. For concrete incorporating G-FBA as a cement replacement and CBA as a fine aggregate replacement, the drying shrinkage was mitigated. The elastic modulus was decreased when RCA and CBA were used in concrete. Additionally, the creep strain of concrete was closely related to its compressive strength and elastic modulus; it decreased with increased compressive strength and elastic modulus. G-FBA, CBA, and RCA can be used as raw materials to make high-strength concrete more environmentally friendly and cost-effective.